The Spinal Cord
To understand what can happen as the result of a spinal cord injury, it is important to understand the anatomy of the spinal cord and its normal functions.
The spinal cord is a tight bundle of neural cells (neurons and glia) and nerve pathways (axons) that extend from the base of the brain to the lower back. It is the primary information highway that receives sensory information from the skin, joints, internal organs, and muscles of the trunk, arms, and legs. The spinal cord then relays this information upward to the brain. The cord also carries messages downward from the brain to other body systems.
Millions of nerve cells situated in the spinal cord itself also coordinate complex patterns of movements such as rhythmic breathing and walking. Together, the spinal cord and brain make up the central nervous system, which controls most functions of the body.
Source: National Institutes of Health
Image source: medicalterms.info
Because the spinal cord is such an important part of our nervous system, it is surrounded and protected by a series of stacked bones (vertebrae) called the spinal column. The spinal cord is about 18 inches long, extending from the base of the brain, down the middle of the back, to about the waist. The spinal column is divided into four sections: (1) at the top are 8 cervical vertebrae; (2) next are 12 thoracic vertebrae; (3) the lower back has 5 lumbar vertebrae; (4) at the bottom are 5 sacral vertebrae fused together into one bone.
The spinal cord after injury
A spinal cord injury (SCI) is one of the most devastating of all traumatic events. In most injuries, bone, ligaments, or disc material pinch the spinal cord causing bruising or a tear in the spinal cord and/or its nerve fibers. After a SCI, all the nerves above the level of injury keep working like they always have. From the point of injury and below, the spinal cord nerves cannot send messages between the brain and parts of the body like they did before the injury.
SCI damage can result in paralysis of the muscles used for breathing; paralysis and/or loss of feeling in all or some of the trunk, arms, and legs; weakness; numbness; loss of bowel and bladder control and sexual function; and numerous long term conditions.
A person's injury is described by its level and type. The level of injury for a person with SCI is the lowest point on the spinal cord below which there is a decrease or absence of feeling and/or movement. The higher the spinal cord injury is on the vertebral column, or the closer it is to the brain, the more effect it has on how the body moves and what one can feel.
Image source: serious-injuries.com
Tetraplegia [formerly called quadriplegia] is the condition of a person with a spinal cord injury in the cervical region causing loss of feeling and/or movement in the head, neck, shoulder, arms and/or upper chest, stomach, hips, legs, and feet.
Paraplegia is the general term describing the condition of a person who has lost feeling and/or is not able to move the lower parts of his/her body.